1. Field of the Invention
The present invention relates to a secondary battery.
2. Description of Related Art
Japanese Patent Application Publication No. 2012-028008 (JP 2012-028008 A) discloses a sealed battery that includes a current interrupt device for cutting off a battery current when an internal pressure of a battery case is increased due to generation of an abnormal gas. The current interrupt device disclosed therein includes a hollow cylindrical electrode terminal that has a flange at one end thereof and a current interrupt valve. The electrode terminal is attached to the battery case in an insulated state while interposing a sealing material in a hole provided in the battery case such that the flange is positioned in the battery case. The current interrupt valve is a convex plate material and is attached to the flange of the electrode terminal so as to project toward an inner side of the battery case. Here, the convex-shaped top of the current interrupt valve is welded to a current collector that is housed in the battery case. A connecting portion of the current collector with the current interrupt valve is thinner than the rest of the portions. The current interrupt valve is a reverse valve and keeps its convex shape that is projected to the inner side of the battery case until the internal pressure of the secondary battery reaches a specified interrupt pressure. Once the internal pressure of the secondary battery exceeds the specified interrupt pressure, the current interrupt valve is reversed (deformed toward the electrode terminal side). At this time, the thinned portion is broken, thereby separating the current collector from the current interrupt valve.
In Japanese Patent Application Publication No. 2008-218193 (JP 2008-218193 A), when the current interrupt valve is reversed (deformed toward the electrode terminal side), the current collector is prevented from being drawn toward the current interrupt valve side, and thus a broken portion of the current collector can be prevented from being deformed and rising toward the current interrupt valve. Accordingly, it is disclosed that the broken portion of the current collector is less likely to contact the current interrupt valve again after the current is interrupted.
Japanese Patent Application Publication No. 09-134715 (JP 09-134715 A) (Japanese Patent No. 3649491) discloses a current interrupt device by which a joined portion between the current interrupt valve and the current collector is separated when the current interrupt valve is reversed. Here, it is disclosed to dispose a compressed elastic member (styrene-butadiene rubber) between the current interrupt valve and the current collector. In this case, it is also disclosed that, after the joined portion between the current interrupt valve and the current collector is separated, the elastic member is elastically returned and expanded to prevent the current interrupt valve and the current collector from being joined to each other again.
For example, like JP 2008-218193 A and JP 09-134715 A (Japanese Patent No. 3649491), various structures to prevent electrical reconnection between the current interrupt valve and the current collector after the current interrupt valve is reversed and the current interrupt valve and the current collector are electrically interrupted have been suggested. In JP 09-134715 A (Japanese Patent No. 3649491), welding of the current interrupt valve and the current collector is peeled when the current interrupt valve is reversed. In other words, it is not a structure in which the current collector is broken and thus the current interrupt valve and the current collector are electrically interrupted when the current interrupt valve is reversed. In addition, JP 2008-218193 A discloses a structure in which the current collector is broken and thus the current interrupt valve and the current collector are electrically interrupted when the current interrupt valve is reversed. However, in this case, the current interrupt valve and the current collector may be electrically reconnected when the current interrupt valve is returned from a reversed condition.